Recent trends of bandwidth hungry application services in cellular communication put tremendous pressure on the network operators to significantly increase the system capacity. Within such perspective, the deployment of femtocells offers reliable and cost effective means to enhance the system capacity and indoor coverage. However, the random deployment of femtocells challenges several technical aspects of the existing cellular systems. The most obvious challenge is the occurrence of interference, which is more severe if spectrum management is not carefully considered. Fractional Frequency Reuse (FFR) has emerged as an attractive interference management technique due to its low complexity and significant coverage improvement. However, most of the previous work analyzes the performance of FFR for perfect geometry based models, whereas no practical deployment has such symmetry. In this paper we investigate the performance of FFR for cellular network based on irregular cell geometry. Furthermore, a novel FFR scheme is proposed for two-tier (macro-femto) network and the capacity of the system is evaluated. It is shown that the proposed scheme outperform the conventional frequency allocation schemes in term of capacity and cell edge performance.